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author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2021-08-04 22:45:36 +0200 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2021-08-05 12:46:42 +0200 |
commit | db243b796439c0caba47865564d8acd18a301d18 (patch) | |
tree | 4d9286e7e1146337ff111a5cf0b2552dc9cc5195 /net/ipv4/ip_sockglue.c | |
parent | Merge branch 'bridge-ioctl-fixes' (diff) | |
download | linux-db243b796439c0caba47865564d8acd18a301d18.tar.xz linux-db243b796439c0caba47865564d8acd18a301d18.zip |
net/ipv4/ipv6: Replace one-element arraya with flexible-array members
There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].
Use an anonymous union with a couple of anonymous structs in order to
keep userspace unchanged and refactor the related code accordingly:
$ pahole -C group_filter net/ipv4/ip_sockglue.o
struct group_filter {
union {
struct {
__u32 gf_interface_aux; /* 0 4 */
/* XXX 4 bytes hole, try to pack */
struct __kernel_sockaddr_storage gf_group_aux; /* 8 128 */
/* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
__u32 gf_fmode_aux; /* 136 4 */
__u32 gf_numsrc_aux; /* 140 4 */
struct __kernel_sockaddr_storage gf_slist[1]; /* 144 128 */
}; /* 0 272 */
struct {
__u32 gf_interface; /* 0 4 */
/* XXX 4 bytes hole, try to pack */
struct __kernel_sockaddr_storage gf_group; /* 8 128 */
/* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
__u32 gf_fmode; /* 136 4 */
__u32 gf_numsrc; /* 140 4 */
struct __kernel_sockaddr_storage gf_slist_flex[0]; /* 144 0 */
}; /* 0 144 */
}; /* 0 272 */
/* size: 272, cachelines: 5, members: 1 */
/* last cacheline: 16 bytes */
};
$ pahole -C compat_group_filter net/ipv4/ip_sockglue.o
struct compat_group_filter {
union {
struct {
__u32 gf_interface_aux; /* 0 4 */
struct __kernel_sockaddr_storage gf_group_aux __attribute__((__aligned__(4))); /* 4 128 */
/* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */
__u32 gf_fmode_aux; /* 132 4 */
__u32 gf_numsrc_aux; /* 136 4 */
struct __kernel_sockaddr_storage gf_slist[1] __attribute__((__aligned__(4))); /* 140 128 */
} __attribute__((__packed__)) __attribute__((__aligned__(4))); /* 0 268 */
struct {
__u32 gf_interface; /* 0 4 */
struct __kernel_sockaddr_storage gf_group __attribute__((__aligned__(4))); /* 4 128 */
/* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */
__u32 gf_fmode; /* 132 4 */
__u32 gf_numsrc; /* 136 4 */
struct __kernel_sockaddr_storage gf_slist_flex[0] __attribute__((__aligned__(4))); /* 140 0 */
} __attribute__((__packed__)) __attribute__((__aligned__(4))); /* 0 140 */
} __attribute__((__aligned__(1))); /* 0 268 */
/* size: 268, cachelines: 5, members: 1 */
/* forced alignments: 1 */
/* last cacheline: 12 bytes */
} __attribute__((__packed__));
This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().
[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/ip_sockglue.c')
-rw-r--r-- | net/ipv4/ip_sockglue.c | 19 |
1 files changed, 10 insertions, 9 deletions
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index 468969c75708..b297bb28556e 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -790,7 +790,8 @@ static int ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval, int optlen) goto out_free_gsf; err = set_mcast_msfilter(sk, gsf->gf_interface, gsf->gf_numsrc, - gsf->gf_fmode, &gsf->gf_group, gsf->gf_slist); + gsf->gf_fmode, &gsf->gf_group, + gsf->gf_slist_flex); out_free_gsf: kfree(gsf); return err; @@ -799,7 +800,7 @@ out_free_gsf: static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval, int optlen) { - const int size0 = offsetof(struct compat_group_filter, gf_slist); + const int size0 = offsetof(struct compat_group_filter, gf_slist_flex); struct compat_group_filter *gf32; unsigned int n; void *p; @@ -813,7 +814,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval, p = kmalloc(optlen + 4, GFP_KERNEL); if (!p) return -ENOMEM; - gf32 = p + 4; /* we want ->gf_group and ->gf_slist aligned */ + gf32 = p + 4; /* we want ->gf_group and ->gf_slist_flex aligned */ err = -EFAULT; if (copy_from_sockptr(gf32, optval, optlen)) @@ -826,7 +827,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval, goto out_free_gsf; err = -EINVAL; - if (offsetof(struct compat_group_filter, gf_slist[n]) > optlen) + if (offsetof(struct compat_group_filter, gf_slist_flex[n]) > optlen) goto out_free_gsf; /* numsrc >= (4G-140)/128 overflow in 32 bits */ @@ -834,7 +835,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval, if (n > sock_net(sk)->ipv4.sysctl_igmp_max_msf) goto out_free_gsf; err = set_mcast_msfilter(sk, gf32->gf_interface, n, gf32->gf_fmode, - &gf32->gf_group, gf32->gf_slist); + &gf32->gf_group, gf32->gf_slist_flex); out_free_gsf: kfree(p); return err; @@ -1455,7 +1456,7 @@ static bool getsockopt_needs_rtnl(int optname) static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval, int __user *optlen, int len) { - const int size0 = offsetof(struct group_filter, gf_slist); + const int size0 = offsetof(struct group_filter, gf_slist_flex); struct group_filter __user *p = optval; struct group_filter gsf; int num; @@ -1467,7 +1468,7 @@ static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval, return -EFAULT; num = gsf.gf_numsrc; - err = ip_mc_gsfget(sk, &gsf, p->gf_slist); + err = ip_mc_gsfget(sk, &gsf, p->gf_slist_flex); if (err) return err; if (gsf.gf_numsrc < num) @@ -1481,7 +1482,7 @@ static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval, static int compat_ip_get_mcast_msfilter(struct sock *sk, void __user *optval, int __user *optlen, int len) { - const int size0 = offsetof(struct compat_group_filter, gf_slist); + const int size0 = offsetof(struct compat_group_filter, gf_slist_flex); struct compat_group_filter __user *p = optval; struct compat_group_filter gf32; struct group_filter gf; @@ -1498,7 +1499,7 @@ static int compat_ip_get_mcast_msfilter(struct sock *sk, void __user *optval, num = gf.gf_numsrc = gf32.gf_numsrc; gf.gf_group = gf32.gf_group; - err = ip_mc_gsfget(sk, &gf, p->gf_slist); + err = ip_mc_gsfget(sk, &gf, p->gf_slist_flex); if (err) return err; if (gf.gf_numsrc < num) |